What is the purpose of a windshield wiper washer fluid in commercial vehicles?

The purpose of windshield wiper washer fluid in commercial vehicles is fundamentally to clear the windshield for better visibility. When driving, especially in adverse weather conditions such as rain, snow, or dirt, the ability to see clearly is paramount for safety. The washer fluid works in conjunction with the wipers to remove grime, debris, and water from the windshield, ensuring that the driver has an unobstructed view of the road. This is essential for making safe driving decisions and maintaining control of the vehicle.

As for the other choices, lubricating the wipers, while helpful, is not the primary function of washer fluid. Cooling the windshield in hot weather might help reduce heat buildup but does not address the immediate concern of visibility which is critical for driving safety. Preventing fogging is generally managed through other means such as climate control or defrost mechanisms, not specifically through washer fluid. Thus, the correct answer emphasizes the importance of visibility enhancement, which is vital for safe operation of a commercial vehicle.